Method of and apparatus for working an oil well



April 26, 1960 F. w. PLEUGER 2,934,728

METHOD OF AND APPARATUS FOR WORKING AN OIL WELL Filed Jan. 2, 1958 2Sheets-Sheet l w 9 24 L J9 J4 40 i a 5 JJ I .72 4/ 25 27 20 26 J6 .70 J7 J/ INVENTOR ATTORNEYS April 26, 1960 Filed Jan. 2, 1958 F. w. PLEUGERMETHOD OF AND APPARATUS FOR WORKING AN OIL WELL 2 Sheets-Sheet 2 ATTO RN EY6 United States Patent P METHOD OF AND APPARATUS FOR WORKING AN OILWELL Friedrich Wilhelm Pleuger, Hamburg, Germany Application January 2,1958, Serial No. 706,770

- Claims priority, application Germany January 7, 1957 8 Claims. (Cl.338-38) This invention relates to the working of oil wells and isespecially concerned with the working of wells where it is desirable ornecessary to employ intermittently operating pumps. The objects andadvantages of the invention will be better understood and more fullyappreciated if the following description of present practices is firstconsidered.

In the method currently in use it is customary from time to time to takemeasurements in the field of the height of the oil column in theindividual bore holes and then to drive the individual pumps at greateror lesser capacity as may be indicated by the results of themeasurements or even to completely shut down the pumps temporarily if itis found that the oil level has dropped excessively. However, the methodjust described has certain inherent disadvantages in that, whenever thepump output is not precisely matched to the quantity of oil that flowsinto the bore hole per unit of time, the pumps have to operate at aconstantly increasing or decreasing load which, of course, preventstheir being utilized at anything nearly approaching their maximumefficiency. A further disadvantage of present practice is that anyexcessive pumping of the oil can be just as detrimental to the flow ofthe oil coming in from the oil bearing stratum as an excessively highoil column. This is particularly troublesome when the output of a wellcontains large proportions of water.

With the foregoing factors in mind, the principal object of my inventionresides in providing a method of and equipment for operating the pump ina manner such that it is started and stopped according to the height ofthe oil column in. the bore as determined by remote measurement of thepressure involved. Furthermore, my invention makes it possible to startand stop the pump entirely automatically by means of a relay systemwhich is directly actuated by the measuring apparatus.

My invention yields a number of, important advantages, the attainment ofwhich constitutes some of the objects of the invention. For instance,with my invention I am enabled to greatly increase the economicalutilization or exploitation of a well. The invention also enables me toobtain a greater rate of flow from a Well than might otherwise beexpected. These objectives are attainable because, with my invention, itis possible to consistently maintain the column of oil in the bore atthe height which yields optimum results not only from the standpoint ofthe quantity of oil to be obtained from a given well but also from thestandpoint of What is best for the long term usefulness of any givenwellf Another object of the invention resides in the provision of amethod of and apparatus for exploiting a well by means of which the pumpis prevented from running idle in the event that the oil column fallsbelow the pumping level.

As an additional feature of the invention, in order to determine thepressure which is proportional to the height of the oil column, a remoteresistance-type sounding or 2,934,728 Patented Apr. 26, 1960 detectingdevice is used whose resistance is altered by the pressure proportionaldisplacement of a mercury column, the resistance being measured aboveground with a crossed coil or parallel coil instrument.

For visual readings and for the control of the pump motor, as willfurther appear, it is advantageous to use a resistance type measuringinstrument whose indications are sensed by a drop-ring or drop-hangerarm because such a movable part can be readily availed of as a means forinitiating or discontinuing the operation of the motor which drives thepump. However, such readings can be sensed in an inertialess manner byelectronic or optical means and in any event, the sensing mechanism cancooperate with adjustable limit or prescribed value markers whereby thecircuit can be engaged or disengaged when deflections occur whichcorrespond to or run beyond the pre-set markers.

In accomplishing the purposes of my invention, I prefer.

to use a resistance type sounding or detecting device in which theresistance is placed in exposed manner in an axial bore of the measuringapparatus housing, which housing is massively constructed of conductivematerial and contains a mercury chamber or reservoir having a movablewall or membrane as will appear more fully hereinafter.

' How all of the foregoing objects and advantages are attained will nowbe described in connection with the accompanying drawings wherein:

' Figure l is an axial section of a temperature and pressure transmitteror detector uesd in connection with my invention;

Figure 2 is a partial axial section similar to that of Figure 1 but onan enlarged scale and illustrating only the lower half of a modifiedtemperature and pressure transmitter; and

Figure 3 is a schematic circuit diagram of an installation for using themethod of my invention.

Referring first to the showing in Figure 3, it will be seen that I haveillustrated a motor 51 for driving the pump of an oil well. The pump isnot specifically illusis exposed to the oil pressure in the bore hole.

but its motor 51 can be placed either above ground in shallow wells andconnected with the bore hole by a suction pipe or can be installeddirectly in the bore hole itself at a point below the'surface of the oilso as to force the oil up through a pipe and out at the top in a mannerwell understood in this art. The pump motor 51 may be started orstopped, i.e., connected to or cut off from a power supply line 54 bymeans of a switch 53 under the control of a relay coil 52, the relay tobe operated in the manner to be described hereinafter so that the oil ispumped out while the oil column height remains at a substantiallyconstant level. When referring to a substantially constant level, i meanto include either a relatively fixed level or one which includes a shortrange of possible variation, say several meters by way of example. Inorder to measure the height of the oil column, a resistance-typesounding or detecting device 55 is lowered into the bore hole thestructure of which device, as will further appear, is of a nature suchthat its resistance will change according to the height of the oilcolumn above it. This sounding device 55 contains a mercury reservoirwhich communicates with an expansion tube and which is sealed off at thebottom with a plastic membrane'or movable wall, the outer side of whichWithin the expansion tube of this sounding device 55, there is aresistancerod which, when the membrane on the mercury reservoir isforced inwardly to a greater or lesser extent by the ambient pressure,can be partially short circuited tothe ground by the mercury rising inthe ex pansion' tube. In this manner, a resistance change can be broughtabout which is proportional to the pressure changes of the oil columnand hence to the height of the oil column. Depending upon the design,the resistance can change linearly or otherwise according to the heightof the oil column.

The amount of resistance in sounding device 55, which thus is anaccurate representation of the height of the oil column above thesounding device, is measured with a crossed coil or parallel coilinstrument 56. The crossed coil instrument 56, which is placed aboveground, is powered from a source of direct current 57. With thisinstrument, the changing resistance of sounding device 55 is comparedwith a standard resistance 58, measuring instrument 56 being socalibrated that it indicates the height of the oil column in the borehole directly upon a scale 59. When it is necessary to make veryaccurate measurements or when greatly varying temperatures pre vail inthe sounding device, the standard resistance 58 may also be installed inthe sounding device so that it is exposed to the same temperatures. Inthis last case, however, three conductors leading to the sounding deviceare required instead of two.

The crossed coil instrument 56- drives indicator 60 across scale 59 inaccordance with the changes in the height of the oil column. Now, inorder to turn pump motor 51 on and off according to the instrumentdeflections, i.e., according to the varying height of the oil column,the position of indicator 60 of measuring instrument 56 is sensedaccording to the drop-hanger principle in a manner known per se. A beamof light or some electronic means can also be used for inertia-lesssensing of indicator 60. On the scale, two independently adjustablelimit-value or prescribed-value markers 61 and 62 are provided, whichestablish those values of the oil column height which are not to beexceeded. In this manner, an operator can set an interval measured inmeters, within which the height of the oil column is permitted to vary.By means of a circuit arrangement which is not shown in detail, butwhich is constructed in a common fashion, the drop-hanger or othersensing member of the measuring instrument brings it about that, as soonas the indicator of the measuring instrument reaches the one limitmarker, switch 63 is closed, and when it reaches the other limit marker,switch 63 is re-opened. Switch 63 controls the power supply 64 to theenergizing circuit of relay coil 52 which opens and closes switch 53.

Of course, it will be understood that instead of the above described twopoint control between the two oil column heights established by thelimit setting device 61 and 62, a single point control may be providedin which switch 63 is closed when a certain oil column height isexceeded and opened when the oil column drops below that same height.This, of course, would be a somewhat more exact type of control, but theprinciple involved is just the same and the accompanying claims areintended to include within their scope either the two point or thesingle point control.

In the case of single-point control the pump can be shut off either whenthe oil level drops below a certain predetermined height, or after acertain period of time which can be predetermined by a time switch. Forthe permanent supervision of the output of an oil well it isparticularly advantageous to record the pumps running and idle time withan automatic recording apparatus.

For the sake of economy, a plurality of resistance-type sounding devicesinstalled in various bore holes can be associated with a commonmeasuring and controlling ap paratus and be connected to the metermechanism in sequence by a periodically operating switching mechanism,the meter mechanism performing the adjustment for each one in turn.

The sounding device preferred for the application of this methodconsists substantially, as shown in Fig. 1, of a massive metal tube 1which is provided with an axial bore'2. Axial bore 2 communicates with achamber 3 filled with mercury. At its outside end, mercury chamber 3 issealed off by a membrane 4, preferably made of plastic. A perforatedmembrane holder 5, which is forced against corresponding membraneclamping surfaces of housing 1 by threaded member 6, serves to fastenmembrane 4 in place. Above the threaded member 6, which is bored throughthe center, membrane 4 is in contact with the fluid enveloping thesounding device. In order that fluid inlet openings 7, which are drilledslantwise, may be freed of any dirt particles that may enter them, cap5; is provided on threaded member 6 and can be unscrewed for cleaningpurposes.

A resistance rod 9 made of graphite is inserted into axial bore 2 so asto be exposed on all sides. At its lower end, rod 9 is supported on anelastic support 10 of open construction, which is clamped into mercurychamber 3. At the other end of rod 9, a metal block 11 is mounted in acorresponding opening in housing 1, with layers of insulating material12 between it and said housing. This metal block 11 is secured in itsposition by means of a head 13 which is screwed into the upper end ofhousing 1 in order to seal the latter. Block 11 has in its center aconductive centering projection 14 which extends into axial bore 2without touching it and serves to center and make electrical contactwith the upper end of resistance rod 9 in the manner of a pointsuspension.

To seal head 13 against the housing 1, a stufiing box system is used,with a gland 14 and packing 15. An insulated conductor 16 is placedcoaxially in head 13 in a hole bored for the purpose, and serves toestablish the connection. with resistance rod 9. The stripped end 17 ofconductor 16 is fastened into metal block 11, by welding or soldering,for example. In order to prevent electrical contact between the strippedconductor end 17 and the metal head 13, the face of head 13 is recessedat 18. A gland 19 which presses packings 20 concentrically about theperiphery of conductor 16 serves to seal the latter against the head.

By means of a coupling 21, which is provided with a tapered thread 22and can be screwed onto head 13 by a thread 23, the entire soundingdevice can be fastened to a drill rod. Conductor 16 is led out ofcoupling 21 through a hole 24. When the apparatus is placed in an oilwell, the pressure of the fluid at the point of measurement causesmembrane 4 to yield. Membrane 4 in turn forces the mercury contained inchamber 3 into the axial bore 2 and thus to a greater or lesser extentshort-circuits the resistance rod 9 to housing 1. The restoring forcefor forcing the mercury back out of axial bore 2 is provided by thevolume of air present in bore 2. The change,

of the resistance in the sounding device can be read overground with acrossed-coil instrument or the like, which is connected on the one handto conductor 16 and on the other hand to the drill rod coupled to themetal housing of the sounding device.

Since the precise resistance of the conductors, i.e., conductor 16 andthe drill rod, must be known in order to achieve a precise measurement,resistance 9 is by-passed by a safety fuse, according to a preferredembodiment, so that the precise electrical resistance of the drill rodmay first be measured before operation is started. Safety fuse 25 isfastened in an axial hole in head 13, said hole being lined withinsulating material. This axial hole in head 13 opens into a cross-hole27 into which an insulated sleeve 28 is screwed. A sharp-pointed contactscrew is inserted into this insulated sleeve 28, said contact screwbeing able with its sharp point to penetrate through the insulation ofthe conductor 16 and create an electrical contact therewith. The radialcross-hole 27 is sealed off externally by a seal screw 30 and a gasket31. As may be seen from the drawing, the bottom end of safety fuse 25rests against contact screw 29, so that the fuse has a direct electricalconnection with conductor 16. At its top end, safety fuse 25 makescontact through a spring 3 2 with a seal screw 33. This seal screw,which is made of metal, creates the contact between the one end of thesafety fuse and the ground, i.e., with the drill rod.

The safety fuse described above by-passes resistance rod 9, so that theresistance of the drill rod can be determined by an initial measurementbetween the upper end of the drill rod and conductor 16, the resistanceof conductor 16 being known. When the resistances are thus known, themeasuring instrument placed above ground can be adjusted. After themeasuring instrument is adjusted, safety fuse 25 can be destroyedby anovercurrent, so that the electrical connection between conductor 16 andthe ground of the sounding apparatus is again broken and the variableresistance 9 is in circuit.

If the measuring system is to be used in conjunction with a non-metallicor poorly conductive drill rod, an additional conductor 34 is connectedto seal screw 33 and secured in place by a set screw 35. It is to beunderstood that the double system shown in the drawing is not necessary,and that it suflices either to connect a conductor 34 electrically tothe coupling screw 33, or to associate the safety fuse 25 with the drillrod.

If in addition to the pressure the temperature at the point ofmeasurement is also to be determined, using the above-described system,a temperature-dependent resistance, an NTC resistor 37, for example, isplaced in an additional'axial hole in head 13, which is lined withinsulating material 36. This resistance 37 is electrically connected atits one end, through a spring 38, with the head 13, while the other endis connected to a separate conductor 39. Conductor 39 leads in the samemanner as conductor 16, and conductor 34, if used, to the instrumentsplaced above ground. The variations of resistance 37 can be measuredbetween conductor 39 and the electrical ground of the drill rod orconductor 34 and be compared with a standard resistance by acrossed-coil instrument in the same manner as resistance 9, in order toobserve the temperature variations. The axial hole for thetemperature-dependent resistance 37 is sealed in the same manner asconductor 16, by a gland 40 which tightly presses packing rings 41against the walls of the hole and the conductor.

In order to assure against the intrusion of oil at very great depths,all the cavities in the sounding apparatus except those serving for theexpansion of the mercury may be filled with oil.

If the sounding device must operate with great accuracy, even whengreatly varying temperatures are encountered, it is possible thaterroneous readings will be provoked due to the difference in the thermalbehavior of the mercury and of the air in bore 2 and chamber 3. In orderto counteract such errors, a compensating device can be provided in theabove ground instruments. By connecting and disconnecting resistance,for example, said compensating device corrects the inidcating circuitaccording to the temperature registered by the temperaturesensitiveresistor 37 in such a manner that an accurate reading is produced.

Magnets can be mounted on the sounding device to hold it in place at thedesired height, instead of using coupling 21. If the sounding deviceaccording to the invention is to measure the gas pressure above the oillevel instead of the oil or water pressure in the oil-bearing stratum,the entire sounding device can be placed on a float in such a mannerthat openings 7, through which membrane 4 is actuated, are kept out ofthe liquid.

Instead of connecting the sounding device with an above groundindicating instrument by means of conductors, a radio transmitter can beinstalled on top of head 13, if desired, and if it is economicallyfeasible, said transmitter being powered by a battery likewise installedin the sounding device andtransmitting the resistance changes from thepetroleum bore hole to a receiver placed above ground.

Another embodiment is represented in Fig. 2, in which the externalpressure is transmitted by a metal bellows 42.

This form of embodiment is used preferably in wells with a large gascontent or where high temperatures prevail, particularly for themeasurement of high pressures.

The use of metal membranes is possible only for small pressure ranges,since the ability of a metal membrane to yield is only slight comparedwith plastic membranes. In order to create a sufficiently great membranemovement at high pressures, the metal membrane must therefore bereplaced by a metal bellows.

The use of plastic membranes is impossible where the gas content and thetemperatures are high, due to the permeability of plastics to gases anddue to their limited ability to withstand heat.

Otherwise, the construction of the model according to Fig. 2 correspondsto that of the embodiment in Fig. 1, and in both figures the parts whichcorrespond with one another are marked with the same reference numbers.A guard tube 43 serves to protect the bellows 42.

It is also pointed out that, instead of the conductors which connect theresistance-type sounding device to meter 56, the pipe through which theoil is pumped to the surface may be used, providing the electricalresistance of this pipe is known.

It will be appreciated that the fully automatic control of the oil levelmade possible by my invention results in more economical utilization ofthe well and, generally, makes it feasible to obtain a greater rate offlow than would be possible otherwise. Furthermore, the invention hasthe additional advantage in that the pump is prevented from running idleshould the oil in the bore fall below the pumping level. It should alsobe noted that, since the method of the invention makes it possible notonly to control the pumping of the well butalso to measure the actualheight of the oil column, the sounding device can be constantly observedand the regulator readjusted according to conditions in the well.Furthermore, recording the running time of the pump makes it possible tosupervise the operation of the sounding device without continuallyobserving the meter.

I claim:

1. A pressure responsive control device for use in controlling the pumpoperation of an oil well, comprising an electrically grounded housingadapted to be inserted in a well and having an axial bore therein; aresistance element of substantial section in said bore but spaced fromthe walls thereof; a mercury chamber below the resistance element incommunication with said bore;

said mercury chamber having a movable wall exposed to when the pressurefalls below a desired value.

2. Apparatus according to claim 1 characterized in that the resistanceelement is an elongated rod formed of graphite.

3. Apparatus according to claim 2 wherein the end of the resistance rodadjacent the mercury is secured to an openly constructed elastic carriermember mounted in the mercury chamber.

4. A pressure sensitive device for use in sensing the pressure of theoil in an oil well, comprising an elongated and massively constructedhousing made of an electrically conductive material and adapted to beinserted into the Well in upright position, the housing including achamber in the lower portion thereof, said chamber having a movable wallexposed to the pressure outside of the housing,

the housing further including an axial bore communicating at its lowerend with said chamber, mercury filling the chamber and rising in theaxial hole in proportion to the pressure applied to the movable wall, astraight unitary resistance rod of substantial cross section extended insaid axial hole, the cross section of the rod being less than that ofthe axial hole, means for mounting the rod centrally in the axial hole,a first electricalv conductor connecting the upper end of the resistancerod with a circuit including a source of electric power, and a secondelectrical conductor connecting the housing with said circuit.

5. A construction according to claim 4 in which the means for mountingthe resistance rod includes an elastic support member extended betweenthe walls of the chamber, said elastic support member being configuredto permit the passage of mercury from the chamber upwardly toward theaxial hole around the edges of the support member.

6. A construction according to claim 4 and further including means fordetermining the resistance of said first electrical conductorcomprising, a fuse interconnecting the housing and said first electricalconductor at a point adjacent the resistance rod.

7. A construction according to claim 4 and further including anelectrically conductive head mounted above the housing and arranged toseal off the upper end of the axial hole, the head including electricalconductor means passing therethrough but insulated therefrom,-the lowerend of the electrical conductor means being in electrical contact withthe upper end of the resistance rod, and a fuse mounted in an insulatedbore in the head, one end of the fuse being electrically connected tothe head by a screw cap adapted to seal one end of the fuse bore, andthe other end of the fuse being electrically connected to a contactscrew having a contact point adapted to pierce the insulationsurrounding the electrical conductor means passing through the head andmake electrical contact with said conductor means.

8. A construction according to claim 4 in which the resistance rod isformed of graphite.

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